This invention generally relates to an auxiliary apparatus for hot-starting an internal combustion engine, and more specifically to such apparatus of the type which while preventing objectionable exhaust of unburned, harmful ingredients of combustible fuel, avoids lowering of engine startabilities caused by a known phenomenon "percolation" that after having stopped the engine of high temperature, some fuel from the carburetor tends to spout into the intake line.
Generally, for the purpose of reducing the amount of harmful chemical substances such as CO, HC, etc. contained in exhaust gases from an automobile engine, there has been known an arrangement wherein secondary air is supplied into the flow of exhaust gas adjacent the exhaust valve on the cylinder head so that unburned ingredients such as CO, HC, etc. carried in the flow of exhaust gas can be burned up, by the secondary air, within a thermal reactor provided downstream from the port wherefrom the secondary air is jetted.
The thermal reactor is usually disposed within the engine room, and therefore the carburetor and other auxiliary equipments will be heated up to high temperatures due to heat transfer from not only the engine but also the thermal reactor where burnings of CO, HC, etc. take place.
In general, the percolation phenomenon is liable to occur in the fuel supply line especially when the engine is brought to a stop with the carburetor being maintained in a high temperature state. Namely, during the engine operation, the interior of the carburetor's float chamber is kept in a state of relatively high temperature and high pressure. As this state remains still for a certain hours even after the engine having stopped, a portion of fuel in the float chamber will be forced out from a main nozzle of the carburetor into the intake line of the engine. The thus expelled portion of fuel, as the engine temperature is gradually lowered, tends to be liquidized and adhere onto the inner wall of the intake manifold.
As long as the engine temperature is high, however, particularly with the engine structure of the type wherein the intake manifold is arranged extending adjacent the exhaust manifold to facilitate heat exchange between both manifolds, such portion of expedded fuel will remain within the intake manifold in the gaseous state under the influence of heat thereat. As a result, the mixture gas in the intake manifold is too rich. Under these conditions, therefore, even if the engine is cranked for starting, there will hardly be smooth starting because of the inferior ignitibility of such rich mixture. Even if the engine is started, unburned ingredients e.g. HC, CO, etc. are undesirably increased in amount.